Medical images are an important component of the medical record generated during a patient's hospital stay or clinic visit, and they are also an important part of the diagnostic and therapeutic phases of a patient's hospital encounter. The National Cancer Institute's Radiation Oncology Branch (ROB) is actively developing a specialized radiotherapy treatment planning system, to suit their protocol requirements. In addition, the NCI ROB is supports a clinical training program jointly with the Walter Reed Army Medical Center (WRAMC) and the National Naval Medical Center (NNMC). For both of these reasons, the NCI ROB is interested in medical image communications and telemedicine systems. The NIH Clinical Center (CC), like most university and research hospitals, is attempting to solve the problem of consolidating medical images with the conventional alphanumeric medical record data in the Medical Information System (MIS) to more completely realize the goal of a comprehensive electronic medical record. DCRT, NCI, and the CC are collaborating to develop a demonstration project that explores image communication and telemedicine technologies. We have implemented a prototype high-speed image communication network based on Asynchronous Transfer Mode (ATM) Switch technology. The ATM Switch allows 155 Mbit/sec multi-media communications between users. This prototype network will initially support high-performance radiation therapy planning, which is a collaborative effort between DCRT's Computational Bioscience and Engineering Laboratory (CBEL) and the NCI ROB. CBEL's IBM SP2 Supercomputer will be utilized to apply the power of parallel computing methods to the implementation of the computationally intensive calculations required for radiation therapy planning. A custom-designed Radiology Consultation Work-Station (RCWS) is currently being developed for use in the NCI ROB, the CC Diagnostic Radiology Department (DRD), and the DCRT environment. Additional RCWS systems will be installed at the WRAMC and the NNMC during FY98. The RCWS allows real-time telemedicine, multimedia conferencing between distributed sites. The RCWS includes high-resolution electronic view boxes for the display of CT, MRI or chest film images. Also included is a high-resolution video link for the presentation of a view of the consultant or the display of video-taped medical images or presentations. The prototype ATM network is connected to the DARPA-funded Advanced Technology Development Network (ATDNet). This ATDNet link will allow collaboration between the NIH and local sites, such as the Walter Reed Army Medical Center and the National Naval Medical Center. Future plans include teleconferencing with the Washington University in St. Louis via the NASA-sponsored ACTS Satellite.